Light-emitting diodes (LED) have become widely used in lighting devices in recent years. With the increasing use of the LED, demands for improved light-extraction efficiency, improved mass production efficiency, and cost reduction have increased in addition to reduction in the size and the thickness of the LED lighting devices. To reduce the size and the thickness of the devices and increase the light-extraction efficiency, semiconductor light-emitting devices that employ a flip-chip mounting have increased. In the flip-chip mounting, an LED element is directly bonded to a lead frame, which is a kind of metal substrates. Employment of the flip-chip mounting allows electrodes of the LED element to be located on the side facing the lead frame. This eliminates shields on the light radiation surface of the LED element and improves the light-extraction efficiency. Since connection leads of the LED element are formed to overlap the LED element, the size is reduced. Elimination of bonding wires further reduces the thickness.
The flip-chip mounting on the metal substrate has increased because the metal substrates are lower in cost compared with common resin substrates and because the metal substrates have superior heat dissipation. The semiconductor light-emitting device that employs the flip-chip mounting on the lead frame, however, has a plurality of connection leads arranged apart from each other in the lead frame to connect to the LED element. With this configuration, the difference in the heights between the connection leads, distortions, and warps are issues that need to be solved. The techniques for solving such issues include, as disclosed in patent document 1, a technique of inserting an electrically insulative reinforcing plate between the connection leads in the lead frame to correct warps.
For semiconductor wafers in other fields, a pre-dicing technique has been proposed to reduce the thickness (patent document 2). The pre-dicing technique includes, first, cutting grooves of a predetermined depth in a semiconductor wafer, backgrinding to allow the grooves to open on the backside, and cutting out semiconductor elements from the semiconductor wafer.